Wedge-shaped free-fall device

ABSTRACT

A free-fall device is disclosed which has a generally wedgeshaped body. Flutes or vanes are provided on all of the triangular faces of the body which cause the body to autorotate and glide when freely falling through the air.

United States Patent Thomas E. Bench;

James H. Coffenberry, both of Richmond, Ind.

Nov. 10, 1969 Oct. 19, 1971 Avco Corporation Richmond, Ind.

Inventors Appl. No. Filed Patented Assignee WEDGE-SHAPED FREE-FALLDEVICE 6 Claims, 5 Drawing Figs.

U.S. Cl 102/4, 102/72, 244/323, 244/137 Int. Cl F42b 25/16 [50]FieldoiSearch 102/2, 4, 7.2;244/3.23, 137,138

[56] References Cited UNITED STATES PATENTS 3,264,985 8/1966 Reed 102/43,332,348 7/1967 Myers et a]. 102/72 Primary ExaminerSamuel W. EngleAttorneys-Charles M. Hogan and Eugene C. Goodale ABSTRACT: A free-falldevice is disclosed which has a generally wedge-shaped body. Flutes orvanes are provided on all of the triangular faces of the body whichcause the body to autorotate and glide when freely falling through theair.

9= ARCTAN LIFT/ DRAG MAGNUS (GLIDE ANGLE FROM THE VERTICAL) LIFT SPINDIRECTION VELOCITY VECTOR INVIL'N'I'URS.

ATTORNEYS.

WEDGE-SHAPED FREEFALL DEVICE BACKGROUND OF THE INVENTION This inventionrelates to free-fall device and more particularly to a free-fall devicehaving a wedge-shaped body which will cause the body to autorotate andglide when free falling through'the air.

When a spinning body, such as a baseball, moves through the air itgenerates a force which is perpendicular to its direction of motion andto the axis of spin. This force is called Magnus force or Magnus lift.In addition, if the falling body has flutes or vanes which produce atorque about its center of gravity while moving through the air, thebody has the ability to spin itself and is said to "autorotate." When anautorotating body is falling free through the atmosphere, its spingenerates Magnus lift and causes the body to glide at an angle from thevertical which is equal to the arctangent of the lift force divided bythe drag force.

In recent years, this concept has been utilized in the manufacture ofaerial mines or bomblets. Generally, a plurality of the bomblets areplaced in a canister or the like and the canister dropped from anaircraft. After a predetermined amount of time, the canister opens andpermits the plurality of bomblets to free-fall. The inherent ability ofthe bomblets to autorotate provides a random ground impact pattern overa large area.

Many different autorotating shapes have been used over the years. Manyshapes do not lend themselves to high packaging density in therespective canister or dispenser. It is of the utmost importance thatthe maximum number of bomblets are incorporated in any given canister inorder to provide maximum bomblet density in the impact area.

Accordingly, it is an object of this invention to provide a free-falldevice which will autorotate and hence glide, and has the addedadvantage of being efficiently packaged.

Another object of this invention is to provide a wedge shaped free-falldevice having aerodynamic means for causing the device to autorotate.

A further object is to provide a free-fall device having an outer shapewhich lends itself for ease of manufacture and provides high packagingdensity for a given canister or dispenser.

SUMMARY OF THE INVENTION BRIEF DESCRIPTION OF THE DRAWINGS Theaccompanying drawings show a present exemplary embodiment of thisinvention in which:

FIG. I is a perspective view illustrating one exemplary embodiment ofthis invention;

FIG. 2 is a top view of the free-fall device of this invention;

FIG. 3 is a side view of the free-fall device of this invention;

FIG. 4 is an end view of a free-fall device of this invention; and

FIG. 5 is a free body diagram of the device of this invention.

DESCRIPTION OF THE ILLUSTRATED EMBODIMENT Reference is now made to thedrawings which illustrate an exemplary embodiment of an improvedfree-fall device or bomblet of the present invention which is designatedgenerally by the reference numeral 10. The free-fall device has a 2housing or casing substantially wedge-shaped and generated by anisosceles triangle. The triangular faces of the device 10 are generallydesignated as 12 and 14 and define substantially rectangular shaped endsurfaces 16 and 18 and a substantially rectangular shaped bottom surface20.

Along all edges of the triangular faces 12 and 14 are aerodynamicelements such as flutes, vanes and the like. The flutes are allaerodynamically situated in the same direction about an axis of rotationor spin axis 22 in order to produce autorotation of the free-fall device10 in the same direction. The spin axis 22 is seen to lie on the centerof gravity of the device 10 and is parallel to the surfaces l2, l4 and20.

The triangular face 14 has a flute 24 along the long .or unequal side ofthe triangle and a flute 26 along each of the short or equal sides ofthe triangular face. Likewise, triangular face 12 has a flute 28 alongthe long or unequal side ofthe triangular face and a flute 30 along theshort or equal sides of the triangular face. It may be seen that eachrespective flute has a reaction surface which for purposes ofexplanation will be designated by the same reference numeral followedbythe letter designation A. As best seen in FIGS. 1 and 4, the freefalldevice 10 has reaction surfaces 24A, 26A, 28A and 30A. Hence, when thefree fall device 10 in the free-fall state, the reaction surfacesrespond or coact with the resistance of' the air to cause the device 10to spin or autorotate about the axis 22 which causes the device 10 toglide at an angle 0 from the vertical. As seen in the free body diagramof FIG. 5, as the free-fall apparatus 10 spins or autorotates, itgenerates a Magnus lift and glides at an angle 0 from the vertical where6=arctan (Lift Force/Drag Force) In operation, a plurality of thefree-fall device 10 are packaged in a suitable canister or dispenserwhich will i be discharged from an aircraft or the like. The canisterwill open a predetermined time after discharge from the aircraft'orthelike to permit each individual device 10 to autorotate i'n order toprovide maximum ground impact patterns.

It can be seen that this invention provides a free-fall device which,because of its geometric wedge-shaped configuration, permits highpackaging density. The shape of the free-fall device of this inventionalso lends itself for ease of manufacture.

has been illustrated and described, it will be recognized that thisinvention may be otherwise variously embodied and practiced by thoseskilled in the art.

What is claimed is:

I. In a free-fall device adapted for release from a canister having aplurality of such devices contained therein, the improved free-falldevice comprising:

a housing having a geometric profile defined as a prism generated bylateral movement of an isosceles triangle, said housing having opposingtriangular faces; and

reaction means along the edges of the triangular faces of the housing tocause the device to spin about an axis of rotation when the device is infree-fall.

2. A free-fall device comprising:

a housing having a generally wedge-shaped isosceles prism configuration,said housing having parallel triangular faces defining generallyrectangular surfaces between the short sides of the triangular faces anda generally rectangular surface between the long sides of the triangularfaces; and

aerodynamic means located on all edges of the triangular surfacesproviding reaction surfaces in order to produce autorotation of thedevice about an axis of rotation in free-fall.

3. A free-fall device as set forth in'claim 2 in which the aerodynamicmeans further comprises flutes along the edges of the triangular faces,said flutes being situated in the same direction about the axis ofrotation to produce autorotation in the same direction; said devicebeing further defined by the axis of rotation being parallel to thetriangular faces and to the long side of the triangular faces.

While a present exemplary embodiment of this invention surfaces, saidflutes being situated in the same direction and providing reactionsurfaces to produce autorotation of the device about an axis of rotationin free-fall.

6. A free-fall device as set forth in claim 5 in which the opposingtriangular faces are isosceles triangular faces, said device beingfurther defined by the axis of rotation being parallel to the triangularfaces and to the long side of the triangular face and the axis ofrotation lies on the center of gravity.

1. In a free-fall device adapted for release from a canister having aplurality of such devices contained therein, the improved free-falldevice comprising: a housing having a geometric profile defined as aprism generated by lateral movement of an isosceles triangle, saidhousing having opposing triangular faces; and reaction means along theedges of the triangular faces of the housing to cause the device to spinabout an axis of rotation when the device is in free-fall.
 2. Afree-fall device comprising: a housing having a generally wedge-shapedisosceles prism configuration, said housing having parallel triangularfaces defining generally rectangular surfaces between the short sides ofthe triangular faces and a generally rectangular surface between thelong sides of the triangular faces; and aerodynamic means located on alledges of the triangular surfaces providing reaction surfaces in oRder toproduce autorotation of the device about an axis of rotation infree-fall.
 3. A free-fall device as set forth in claim 2 in which theaerodynamic means further comprises flutes along the edges of thetriangular faces, said flutes being situated in the same direction aboutthe axis of rotation to produce autorotation in the same direction; saiddevice being further defined by the axis of rotation being parallel tothe triangular faces and to the long side of the triangular faces.
 4. Afree-fall device as set forth in claim 3 in which the axis of rotationlies on the center of gravity.
 5. In a free-fall device adapted forrelease from a canister having a plurality of such devices containedtherein, the improved free-fall devices comprising: a housing having agenerally wedge-shaped configuration, said housing having opposingtriangular faces defining a generally rectangular surface between therespective sides of the triangular faces; and aerodynamic flutes locatedon all edges of the triangular surfaces, said flutes being situated inthe same direction and providing reaction surfaces to produceautorotation of the device about an axis of rotation in free-fall.
 6. Afree-fall device as set forth in claim 5 in which the opposingtriangular faces are isosceles triangular faces, said device beingfurther defined by the axis of rotation being parallel to the triangularfaces and to the long side of the triangular face and the axis ofrotation lies on the center of gravity.